This invention relates to an ink drop writing apparatus and more particularly to an improved ink drop writing apparatus free from the print distortion.
Apparatus has been developed for printing on a writing medium of the information represented by video signals by generating a stream of ink drops, directing these ink drops toward the writing medium, and then, deflecting the ink drops in response to the video signal, in a manner so that when the ink drops reach the writing medium, they provide a representation of the information contained in the video signals. The general apparatus employed for producing the ink drops consists of an ink reservoir in which there is ink under pressure. The ink reservoir feeds a pipe which is connected to a nozzle.
An electromechanical transducer is employed to vibrate the pipe and the nozzle at some suitable high frequency which causes the ink to be injected from the nozzle in a stream which shortly thereafter breaks into individual drops.
In the region just before the stream breaks into drops there is placed a charging tunnel through which the stream is projected, which serves the function of applying video signals to the individual drops. Downstream of the tunnel there is provided a pair of deflection plates which have a fixed potential thereacross. The electric field which is created between the plates acts on the charged drops causing them to be deflected in an amount determined by the amplitude of the charge on the drops. Downstream of the deflection plates is usually a gutter or trough for catching any drops which do not have any charge and transferring them to a waste reservoir. There is also positioned downstream of deflection plates the writing medium which is to receive the deflected ink drops, which thereby form the images representative of the video signals. The writing medium is usually moved in synchronism with the application of video signals to the drops.
In the printing apparatus of the type briefly discribed above, when the writing ink drops are continuously used as the pattern formation ink drops, the ink drops are not able to be given a desired amount of charge and deflection and therefore form writing dots on positions deviated from the correct positions. As a result, the writing deformation occurs. The cause of the deformation is an electrostatic and aerodynamic interference between the pattern formation ink drops.
In the conventional apparatus as shown in U.S. Pat. No. 3,562,757 issued to Bischoff on Feb. 9, 1971, every Nth drops (N is a natural number) injected from the nozzle are used as the writing ink drops and the remaining drops produced between the writing ink drops are not charged. Drops without a charge are discarded as dummy or guard drops to broaden the gap between the character pattern formation ink drops so as to reduce the interference therebetween. This apparatus, however, has the drawback that the writing speed of characters is greatly reduced to 1/n+1 of the former speed.